TYPHOID VACCINATION

  

TYPHOID VACCINATION

Currently recommended vaccines are:

1. Oral typhoid vaccine: Oral S.typhi (Typhoral), and
2. Injectable Vi capsular polysaccharide typhoid vaccine (Typhim Vi, Vac Typh, Typhivax, Typho Vi, Tyvax-Vi)
3. Classical: Whole-cell killed. TA vaccine as it also includes S.Paratyphi A.

Oral typhoid vaccine It contains Ty 21 live attenuated mutant strains of S, typhosa. The dose is one capsule on day 1,3 and 5 one hour before a meal, given every 3 years. The vaccine is well tolerated; rarely slight gastrointestinal upset and rash may occur. It confers a protection varying from 67 to 95%. Storage between 2 to 8 degree C and protection from light is vital for its stability.

Contraindications include immunodeficiency, immunosuppressant drugs, antimitotics, certain antibiotics and sulfas active against salmonella, acute febrile illness, GIT infection, and pregnancy.

Polysaccharide Vi typhoid vaccine It contains purified Vi capsular polysaccharide (ViCPS). The dose is one injection (0.5 ml containing 25 meg of ViCPS) given SC or IM as a single dose every 3 years. It confers a protection of 75 to 100%. Only mild local pain and fever may rarely occur as side-effects. Contraindications include hypersensitivity and pregnancy.

Ideally, for maximal protection, these vaccines are recommended to be administrated after 5 to 6 years of age. Nevertheless, in view of increasing occurrence of typhoid fever under 5 years of age, starting typhoid immunization at 18-24 months with injectable vaccine in endemic areas is justified.

Whole cell killed TA vaccine is quite cheap (though at present its production is suspended). It is given in two doses 0.25 – 0.5 ml each (SC) at an interval of 4-6 weeks, starting at 6 months of age or later. However, it is likely to cause side-effects such as local pain and induration, pyrexia and body pains over the next 2-3 days. Reactogenicity is less in Monovalent (Containing endotoxin of S.typhi only) vaccine, acetone killed and dried preparation (AKD vaccine). Revaccination every 3 years is needed.

The following improved new typhoid vaccines which can be given to the infants too are under clinical trial:

1. Genetically engineered strains of S.typhi as single dose live oral vaccines having higher immunogenicity over Ty 21 a.
2. Parenteral Vi-conjugate vaccine that stimulates higher titers of Vi antibodies than conjugated Vi polysaccharide and elicts immunologic memory.

Whole cell (conjugated) typhoid vaccine is safe and can be given to even infants.